Sorry, a little late to the party - okay a lot late, but when I went to that 4 day seminar on Understanding K9 Behavior, I learned a great technique. It goes like this...
At the first sign of focus or arousal, step in front of your dog and tell them "no" on a deep voice, serious voice and here is the important part...use your body to pressure them to move AWAY FROM the thing they were focusing on. You may need to keep the pressure or add pressure (by continuing to move into their space). When they move away, release your body pressure. If they are really aroused or if your timing is off and your didn't catch them at the first alert, you may need to add a sound or event to startle them so that they break their focus on the object/person and look at you.
Prior to me using this technique, whenever someone would come to my door or even walk past the house, with over 300 lbs of dog, you would think that Armageddon had arrived and all hell would break loose at my front window. After using this technique for about a week, I could STOP (and I mean stop ALL barking and all charging) with the "No."
Now the window is open so that they watch the person approach or pass and I can praise them for remaining quiet and calm and there are no reactions! If someone forgets, a simple, "no" stops them.
I have found it to be incredibly powerful!